#id: identification of data frames
#cmd: calculate steer angle using
#steer_dir: 0:auto(self judgment); 1:positive  2:opposite  
#prohibit_limit_flip: true: steer can not auto flip  when steer reach to limit; false: self judgment
#open:Is the current command steering enabled
#steer_dir宏定义
uint8 DIR_AUTO     = 0
uint8 DIR_POSITIVE = 1
uint8 DIR_OPPOSITE = 2

uint64               id
geometry_msgs/Twist  cmd
int32                steer_dir
bool                 prohibit_limit_flip
bool                 open